Networks that provide wireless access may include wireless backhaul connectivity between network nodes, for example using microwave signals. The microwave signals are transmitted with enough power to achieve an acceptable Signal to Noise Ratio (SNR). The required power level depends on channel conditions. For instance, during favorable channel conditions, the microwave signals may be transmitted with relatively low power. Conversely, in poor channel conditions, the microwave signals may need to be transmitted with relatively high power.
However, transmitting the microwave signals with too much power can result in interference between adjacent channels. As such, the microwave signals are subject to a spectral mask, which defines a maximum allowed transmit power over a range of frequencies as a function of frequency. The spectral mask is generally intended to reduce interference between adjacent channels by limiting transmission power. Spectral masks have been defined by various standardization bodies such as the International Telecommunication Union (ITU), the Federal Communications Commission (FCC), the Electronic Communications Committee (ECC), the European Conference of Postal and Telecommunications Administrations (CEPT), the European Telecommunications Standards Institute (ETSI) and other standardization bodies.
When microwave signals are transmitted with relatively low power, the microwave signals can be transmitted with wider bandwidth while still complying with the spectral mask. There is a desire to achieve improved spectral efficiency in these wider bandwidth transmissions.